Sienna Miller hit the Live By Night red carpet on Wednesday in London, England, wearing a lovely black and cream-colored Lanvin gown, but inevitably got cold while posing in the 50-degree weather. Her co-star, Ben Affleck, came to her rescue and loaned her his black overcoat while she chatted with the press. Meanwhile, Affleck made do with his navy blue suit jacket.

Live By Night, which debuts in theaters on Friday, is set in the Prohibition Era and centers around a group of individuals and their dealings in the world of organized crime.

Getty Images

Getty Images

Miller, 35, appears very comfortable with Affleck, 44, on the red carpet, but admitted to ET that she got a little star struck at Sunday's Golden Globes when she found herself chatting with her co-star and his A-list actor friends. “I found myself backstage in a kind of semi-huddle with Brad Pitt, Ben Affleck, and Jon Hamm, which was quite surreal. It was exciting,” she gushed. "I have a mental photo that I will hold onto!”